Most hydrocarbon producing wells employ a downhole pump which is reciprocated by a rod string. The rod string is actuated by a pumpjack unit. The downhole pump includes a piston, or a plunger, within which a traveling valve is incorporated. The piston reciprocates within a pump barrel, and a standing, or fixed valve is placed below the pump barrel. As the sucker rod string reciprocates the pump piston, fluid is lifted to the surface of the earth.
From time to time debris will accumulate under either the traveling or fixed valve, thereby preventing the valve element from properly seating, and consequently, the pumping action will be greatly reduced and in many instances, the pumping action will altogether cease. This same malfunction occurs whenever compressible fluid accumulates between the valves of the pump assembly, and causes a condition referred to as fluid pounding, or gas lock, to arise.
In the past, those skilled in the art of producing oil wells with pumpjack units have discovered that the stuck pump valves sometime can be jarred loose, or that the valves can be jarred to pass the gas through the pump. This is accomplished by de-energizing the pumpjack unit, after which the rod clamp is repositioned on the polish rod at a particular location which enables the downhole pump piston to strike or impact against the pump barrel. This adjustment is critical, and a considerable amount of time and expertise is required in order to properly bump the piston against the barrel without injuring the downhole equipment.
After the downhole pump has been bumped in the above described manner, the rod clamp is returned to its original position respective to the polish rod, and the well pumpjack unit is again energized. In the event the debris has not been dislodged from the valve assemblies, it is necessary to repeat the entire operation. The same holds true for the gas lock condition. This procedure must therefore be carried out until the well is again satisfactorily producing the downhole fluid.
Usually four men are required to work the better part of an hour in order to bump a well. One procedure used in the past is to place a second polish rod clamp on the polished rod, and manipulate the walking beam in a manner to enable the first clamp to be moved up the polish rod until the string is spaced out an appropriate amount to achieve the desired impact from the resultant bumping action. The pumpjack unit is then energized so that the downhole pump is bumped for awhile, and thereafter the polish rod clamp must be returned to its original position by reversing the above procedure. Needless to say, many a workman's hand has inadvertently been caught under a clamp and severely injured. Furthermore, four workmen manipulating a pumpjack unit creates various different unsafe conditions wherein numerous other occasions for possible injury arises.
In some instances, the technicians will repeat the procedures many times, and eventually, if the well pump fails to satisfactorily respond to the bumping treatment, it is necessary to pull the rod string and investigate the condition of the traveling valve. If the trouble lies with the standing valve, it is necessary to pull the production string and pump barrel, and clean the debris from the standing valve. This is a very expensive procedure and sometimes requires an expenditure of several thousand dollars.
It would therefore be desirable to be able to precisely control the relative position of the pump piston and pump barrel so that the well can be bumped under closely controlled conditions, and thereafter be placed back into operation safely with a minimum amount of labor and abuse to the downhole equipment.
Method and apparatus which achieve the above desirable goal is the subject of the present invention.